ChemComm View Article Online

Published on 24 February 2014. Downloaded by WASHBURN UNIVERSITY on 29/10/2014 15:33:33.

COMMUNICATION

View Journal | View Issue

Cite this: Chem. Commun., 2014, 50, 3976

A copper-catalyzed formal O–H insertion reaction of a-diazo-1,3-dicarbonyl compounds to carboxylic acids with the assistance of isocyanide†

Received 17th January 2014, Accepted 24th February 2014

Zikun Wang,a Xihe Bi,b Yongjiu Liang,*a Peiqiu Liaob and Dewen Dong*a

DOI: 10.1039/c4cc00402g www.rsc.org/chemcomm

A novel copper-catalyzed formal O–H insertion of a-diazo-1,3dicarbonyl compounds to carboxylic acids has been developed, providing a straightforward synthetic method for a-acyloxy-1,3dicarbonyl compounds, in which the activation of carboxylic acids by isocyanide plays a crucial role.

a-Diazocarbonyl compounds have proved to be versatile precursors of carbenes under thermolytic, photolytic, or transition metalpromoted reaction conditions.1 Owing to their ease of preparation and handling,2 a diverse range of a-diazocarbonyl compounds have been employed in the cyclization,3 ylide transformation,4 the Wolff rearrangement5 and X–H insertion (X = O, N, S, C or Si)6 reactions for the synthesis of complex organic molecules. Recently, Basso and co-workers developed a Passerini-like 3-component reaction of a carboxylic acid, an isocyanide and a ketene or an a-diazocarbonyl compound to access stereodefined captodative olefins, which was defined as K-3CR (Scheme 1).7 During the course of our studies on the utilization of a-diazo-b-oxoamides in organic synthesis, we achieved the synthesis of 1,2,3-triazoles and pyrrol-3(2H)-ones in the presence of different catalysts.8 It is worth noting that a-diazo-b-oxoamides could be transformed into ketene intermediates catalyzed by copper(II). Inspired by this finding, we envisaged that captodative olefins might be synthesized from a-diazo-b-oxoamides, isocyanides and carboxylic acids (Scheme 1). After a series of experiments, we found that a formal O–H insertion product of a-diazo-1,3-dicarbonyl compound to carboxylic acid instead of captodative olefin was obtained (Scheme 1). a-Acyloxycarbonyl compounds as significant building blocks in synthetic organic chemistry are traditionally prepared by the substitution reaction of a-halodicarbonyl compounds with alkaline carboxylates,9 the direct oxidative coupling of carbonyl compounds a

Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, 130022, China. E-mail: [email protected], [email protected] b Department of Chemistry, Northeast Normal University, Changchun, 130024, China † Electronic supplementary information (ESI) available: Experimental procedures, analytical data, and copies of spectra of all compounds. See DOI: 10.1039/c4cc00402g

3976 | Chem. Commun., 2014, 50, 3976--3978

Scheme 1

The isocyanide-based 3-component reactions.

with acids mediated by hypervalent iodine reagents10 or toxic heavy metal oxidants,11 such as Pb(OAc)4,12 Tl(OAc)3,13 and Mn(OAc)3,14 or the formal O–H insertion reactions of a-diazocarbonyl compounds to carboxylic acids.15 Among these methods, the latter has displayed outstanding advantages with regard to fabricating the a-acyloxycarbonyl compounds including (1) mild reaction conditions; (2) high chemo-selectivity; (3) inexpensive and readily available starting materials. However, it is a challenge to synthesize the closely related a-acyloxy-1,3-dicarbonyl scaffolds using this method due to the relative instability of a-diazo-1,3-dicarbonyl compounds,1,16 and expensive catalysts based on Pd or Rh are necessary to decompose the diazo group in most cases.15g,h In the present work, we wish to describe a straightforward procedure to access a-acyloxy-1,3dicarbonyl compounds via a copper-catalyzed formal O–H insertion reaction of a-diazo-1,3-dicarbonyl compounds to carboxylic acids with the assistance of isocyanide. The reaction of a-diazo-b-oxoamide 1a, acetic acid 2a and isocyanides was examined under different conditions (Table 1). When 1a and CNCH2Ts (1.0 equiv.) were allowed to react with acetic acid at 100 1C in the presence of Cu(AcO)2 (0.1 equiv.), the reaction proceeded smoothly to furnish a product characterized as

This journal is © The Royal Society of Chemistry 2014

View Article Online

Communication

Published on 24 February 2014. Downloaded by WASHBURN UNIVERSITY on 29/10/2014 15:33:33.

Table 1

ChemComm

Screening of conditionsa

Entry

Cu

Isocyanide (equiv.)

Solvent

T (1C)

Time (h)

Yieldb (%)

1 2 3 4 5 6 7 8 9 10 11c 12c

Cu(AcO)2 Cu(AcO)2 Cu(AcO)2 Cu(AcO)2 Cu(AcO)2 CuSO4 Cu(acac)2 CuBr2 CuI Cu(AcO)2 Cu(AcO)2 Cu(AcO)2

CNCH2Ts (1.0) none CNCH2COOEt (1.0) CNCH2COOEt (0.5) CNCH2COOEt (0.3) CNCH2COOEt (0.5) CNCH2COOEt (0.5) CNCH2COOEt (0.5) CNCH2COOEt (0.5) CNCH2COOEt (0.5) CNCH2COOEt (0.5) CNCH2COOEt (0.5)

None None None None None None None None None None DMF Ethyl acetate

100 100 100 100 100 100 100 100 100 80 100 Reflux

5 10 5 5 5 6 7 4 4 10 10 10

77 N.R. 84 83 71 46 43 Unidentifed mixture Unidentifed mixture Trace N.R. N.R.

a

Reagents and conditions: 1a (1.0 mmol), 2a (4.0 mL), copper salts (0.1 mmol).

1,3-dioxo-1-(phenylamino) butan-2-yl acetate (77% yield) on the basis of its analytical data (Table 1, entry 1). Obviously, CNCH2Ts did not act as a reactant in the reaction system. Thus, as a control experiment, the same reaction excepting the inclusion of isocyanide exhibits no reaction (entry 2). These results suggested that isocyanide played a key role in the transformation process. It was found that the yield of 3a could reach 84% when ethyl isocyanoacetate was employed (entry 3). The decrease of isocyanide to 50 mol% had no significant effect on the conversion (entry 4), while a further decrease of isocyanide would reduce the yield of 3a (entry 5). In the presence of CuSO4 or Cu(acac)2, the reaction of 1a and acetic acid could proceed, but the conversion was very low (entries 6 and 7), whereas in the presence of CuBr2 or CuI, an unidentified complex mixture was obtained (entries 8 and 9). It should be noted that the reaction of 1a and acetic acid could almost not proceed when conducted at 80 1C (entry 10). No reaction was observed as indicated by TLC results when 1a, ethyl isocyanoacetate (0.5 equiv.), acetic acid (5.0 equiv.) and Cu(AcO)2 (0.1 equiv.) were allowed to react in DMF or ethyl acetate (entries 11 and 12). With the optimized conditions in hand, a series of reactions of a-diazo-b-oxoamides 1b–i bearing varied alkyl and aryl groups R1 and aryl amide groups R2 with acetic acid were carried out. As shown in Table 2, all the reactions proceeded smoothly to afford the corresponding a-acyloxy carbonyl compounds 3b–i in good to high yields (entries 1–8). The synthetic efficiency was evaluated by reacting a-diazo-b-dicarbonyls 1j, 1k and 1l with ketone and ester groups (COR2) and acetic acid under the identical conditions (entries 9–11). Next, we examined the reactions of miscellaneous carboxylic acids with a-diazo-b-oxoamide 1a, and some of the results are summarized in Scheme 2. The synthesis of the a-acyloxy carbonyl compound was proved to be suitable for the saturated and unsaturated carboxylic acids. As previously mentioned, substrate 1a failed to react with acetic acid in the absence of isocyanides, demonstrating that an isonitrilic species is crucial for the success of the process. To further investigate the effect of isocyanides, some experiments were conducted. Firstly, 2-isocyanoacetate (0.5 mmol) and acetic acid (4.0 mL) were mixed under stirring and kept at 100 1C for 1.0 h.

This journal is © The Royal Society of Chemistry 2014

b

Isolated yields. c AcOH (5.0 mmol) was added.

Table 2 Synthesis of a-acyloxycarbonyl compounds 3 from a-diazo-1,3dicarbonyl compounds and acetic acida

Entry

1

R1

R2

3

Yieldb/%

1 2 3 4 5 6 7 8 9 10 11

1b 1c 1d 1e 1f 1g 1h 1i 1j 1k 1l

Me Me Me Me Me Me n-Pr Ph Me Ph Ph

4-MeC6H4NH 2-MeC6H4NH 4-ClC6H4NH 2-ClC6H4NH 4-CF3C6H4NH 2,4-Me2C6H3NH C6H5NH C6H5NH OEt OEt Me

3b 3c 3d 3e 3f 3g 3h 3i 3j 3k 3l

82 77 81 79 75 73 86 78 83 69 74

a

Reagents and conditions: 1 (1.0 mmol), 2a (4.0 mL), Cu(OAc)2 (0.1 mmol), ethyl isocyanoacetate (0.5 mmol), 100 1C, 4.0–5.0 h. b Isolated yields.

Scheme 2 The O–H insertion reactions of a-diazo-b-oxoamide 1a with different carboxylic acids. Reagents and conditions: 1a (1.0 mmol), 2 (4.0 mL), Cu(OAc)2 (0.1 mmol), ethyl isocyanoacetate (0.5 mmol), 100 1C, 4.0–5.0 h.

The H1 NMR analysis of the resulting mixture indicated that ethyl isocyanoacetate was consumed, and an active intermediate A

Chem. Commun., 2014, 50, 3976--3978 | 3977

View Article Online

ChemComm

Communication

Published on 24 February 2014. Downloaded by WASHBURN UNIVERSITY on 29/10/2014 15:33:33.

Notes and references

Scheme 3

Probing the effect of isocyanide.

Scheme 4

A plausible reaction mechanism.

seemed to be formed (Scheme 3). It is worth noting that 3a could be obtained in 79% yield when 1a (1.0 equiv.) and Cu(OAc)2 (0.1 equiv.) were added to the above mixture and stirred at 100 1C for 4.0 h. In another experiment, after the solution of ethyl isocyanoacetate (0.5 mmol) in acetic acid (4.0 mL) was run at 100 1C for 10 h, formamide B was obtained in 82% yield. It is interesting to note that no desired 3a was obtained when 1a (1.0 equiv.) and Cu(OAc)2 (0.1 equiv.) were added to the mixture or treated with B (0.5 equiv.) in acetic acid at 100 1C. Actually, the reaction of isocyanides and carboxylic acids was also reported via microwave irradiation or thermolytic activation to produce formamides and anhydrides.17 On the basis of all the results obtained and the literature, a plausible mechanism for the formal O–H insertion reaction of a-diazo-1,3-dicarbonyl compounds to carboxylic acids is proposed.18 As shown in Scheme 4, the reaction of carboxylic acid and isocyanide takes place to produce the intermediate A. In the presence of Cu(AcO)2 at high temperature, a Cu-carbene C is generated from a-diazo-1,3-dicarbonyl compound 1, which then reacts with A to give an ylide intermediate D.19 Then, intermediate D takes a proton from carboxylic acid 2 and undergoes a nucleophilic addition–elimination reaction with the carboxylate to afford a-acyloxy-1,3-dicarbonyl compound 3 along with the regeneration of A. In conclusion, a novel Cu(II)-catalyzed and isocyanide-assisted formal O–H insertion reaction of a-diazocarbonyl compounds to carboxylic acids has been developed, which provides a straightforward synthetic access to a-acyloxycarbonyl compounds and describes an unprecedented reaction pattern in the chemistry of O–H insertion.

3978 | Chem. Commun., 2014, 50, 3976--3978

1 For selected reviews, see: (a) T. Ye and M. A. Mckervey, Organic Synthesis with a-Diazo Carbonyl Compounds, Chem. Rev., 1994, 94, 1091; (b) M. P. Doyle, M. A. Mckervey and T. Ye, Modern Catalytic Methods for Organic Synthesis with Diazo Compounds, Wiley, New York, 1998. 2 For examples on synthesis of diazo compounds, see: (a) M. Regitz, Angew. Chem., Int. Ed. Engl., 1967, 6, 733; (b) G. Maas, Angew. Chem., Int. Ed., 2009, 48, 8186. 3 (a) D. Artt, M. Jautelat and R. Lantzsch, Angew. Chem., Int. Ed. Engl., 1981, 20, 703; (b) J. A. Marshall, J. C. Peterson and L. Lebiods, J. Am. Chem. Soc., 1983, 105, 6515; (c) E. Y. Chen, Tetrahedron Lett., 1982, 23, 4769E. Y. Chen, J. Org. Chem., 1984, 49, 3245. 4 (a) L. Malatesta and F. Bonati, Isocyanide Complexes of Metals, Wiley, London, 1969; (b) P. M. Treichel, Adv. Organomet. Chem., 1973, 11, 21; (c) F. Bonati and G. Minghetti, Inorg. Chim. Acta, 1974, 9, 95; (d) Y. Yamamoto, Coord. Chem. Rev., 1980, 32, 193; (e) E. Singleton and H. E. Oosthuizen, Adv. Organomet. Chem., 1983, 22, 209. 5 W. Kirmse, Eur. J. Org. Chem., 2002, 2193. 6 S.-F. Zhu and Q.-L. Zhou, Acc. Chem. Res., 2012, 45, 1365. 7 A. Basso, L. Banfi, S. Garbarino and R. Riva, Angew. Chem., Int. Ed., 2013, 52, 2096. 8 (a) Z. Wang, X. Bi, P. Liao, R. Zhang, Y. Liang and D. Dong, Chem. Commun., 2012, 48, 7076; (b) Z. Wang, X. Bi, P. Liao, X. Liu and D. Dong, Chem. Commun., 2013, 49, 1309. 9 P. A. Levine and A. Walti, Org. Synth. Coll., 1943, II, 4843. 10 For reviews, see: (a) V. V. Zhdankin, Chem. Rev., 2002, 102, 2523; (b) V. V. Zhdankin, Chem. Rev., 2008, 108, 5299For selected examples, see: (c) W.-B. Liu, C. Chen, Q. Zhang and Z.-B. Zhu, Beilstein J. Org. Chem., 2011, 7, 1436; (d) J. Yu, J. Tian and C. Zhang, Adv. Synth. Catal., 2010, 352, 531. 11 For reviews, see: (a) D. J. Rawilson and G. Sosnovsky, Synthesis, 1973, 567; (b) D. J. Rawlinson and G. Sosnovsky, Synthesis, 1972, 1. 12 (a) T. Satoh, S. Motohashi and K. Yamakawa, Bull. Chem. Soc. Jpn., 1986, 59, 946; (b) C. Walling and J. Kjellgren, J. Org. Chem., 1969, 34, 1488; (c) E. I. Heiba, R. M. Dessau and W. J. Koehl, J. Am. Chem. Soc., 1968, 90, 1082; (d) E. I. Heiba, R. M. Dessau and W. J. Koehl, J. Am. Chem. Soc., 1969, 91, 138. 13 (a) M. E. Kuehne and T. C. Giacobbe, J. Org. Chem., 1968, 33, 3359; (b) J. C. Lee, Y. S. Jin and J.-H. Choi, Chem. Commun., 2001, 956; (c) S. Uemura, T. Nakano and K. Ichikawa, Nippon Kagaku Zasshi, 1967, 88, 1111. 14 (a) G. J. Williams and N. R. Hunter, Can. J. Chem., 1976, 54, 3830; (b) J. M. Davidson and C. Triggs, J. Chem. Soc. A, 1968, 1331; (c) P. J. Andrulis, M. J. S. Dewar, R. Dietz and R. L. Hunt, J. Am. Chem. Soc., 1966, 88, 5473; (d) L. Eberson, J. Am. Chem. Soc., 1967, 89, 4669. 15 For examples on O–H insertion reactions of a-diazocarbonyls to carboxylic acids, see: (a) M. L. Wolfrom, A. Thompson and E. F. Evans, J. Am. Chem. Soc., 1945, 67, 1793; (b) J. L. E. Erickson, J. M. Dechary and M. R. Kesling, J. Am. Chem. Soc., 1951, 73, 5301; (c) R. Paulissen, H. Reimlinger, E. Hayez, A. J. Hubert and ´, Tetrahedron Lett., 1973, 14, 2233; (d) P. J. Giddings, Ph. Tehssie D. I. John and E. J. Thomas, Tetrahedron Lett., 1978, 995; (e) T. Shinada, T. Kawakami, H. Sakai, I. Takada and Y. Ohfune, Tetrahedron Lett., 1998, 39, 3757; ( f ) N. Jiang, J. Wang and A. S. C. Chan, Tetrahedron Lett., 2001, 42, 8511; ( g) S. Bertelsen, M. Nielsen, S. Bachmann and K. A. Jørgensen, Synthesis, 2005, 2234; (h) M. Kitamura, M. Kisanuki, R. Sakata and T. Okauchi, Chem. Lett., 2011, 40, 1129. 16 H. M. L. Davies and R. E. J. Beckwith, Chem. Rev., 2003, 103, 2861. 17 (a) X. Li and S. J. Danishefsky, J. Am. Chem. Soc., 2008, 130, 5446; (b) J. Hou, D. Ajami, Jr. and J. Rebek, J. Am. Chem. Soc., 2008, 130, 7810; (c) A. Shaabani, E. Soleimani and A. H. Rezayan, Tetra¨dgam and H. Hartl, hedron Lett., 2007, 48, 6137; (d) D. Lentz, I. Bru Angew. Chem., Int. Ed. Engl., 1987, 26, 921; (e) D. Lentz, Angew. Chem., Int. Ed. Engl., 1994, 33, 1315. 18 (a) M. C. Pirrung, H. Liu and A. T. Morehead, J. Am. Chem. Soc., 2002, 124, 1014; (b) D. Gillingham and N. Fei, Chem. Soc. Rev., 2013, 42, 4918. 19 For a recent review on copper–carbene, see: X. Zhao, Y. Zhang and J. Wang, Chem. Commun., 2012, 48, 10162.

This journal is © The Royal Society of Chemistry 2014

A copper-catalyzed formal O-H insertion reaction of α-diazo-1,3-dicarbonyl compounds to carboxylic acids with the assistance of isocyanide.

A novel copper-catalyzed formal O-H insertion of α-diazo-1,3-dicarbonyl compounds to carboxylic acids has been developed, providing a straightforward ...
998KB Sizes 2 Downloads 3 Views